Grained, patterned, or finely structured plastic skins forming surfaces for objects are widely known and are used for example for the interior trim in motor vehicles, often in the form of relatively soft, underfoamed films with a pleasing feel, for instance for the trim of dashboards or the interior shells of doors, et cetera. With appropriate adaption in terms of strength and design, such films are of course also used for other articles that are provided with a high-quality coating.
There are various methods known in the art for producing such plastic skins, for example rolling and/or embossing methods for producing “endless” film webs of thermoplastic material, or methods for producing individual out of tool molded skins, that is to say plastic moldings.
In the case of the rolling and embossing methods, an embossing roller is used to provide a thermoplastic film in the form of a web with a three-dimensionally structured, embossed surface, that is to say for instance a grained “leather surface.”
Out of tool molded skins in this context refer to more or less rigid plastic moldings which, for example, are produced in molds by various sintering or spraying processes, and in the case of which one or more liquid or powdered components are introduced into a mold and react/cure there. Out of tool molded skins are consequently also created by rotational sintering, for example by methods for producing so-called slush skins.
In the case of these out of tool methods there is also the possibility of determining the surface structure/texture, that is, the surface of the plastic skin, that is to say for example the appearance of a grain effect, and the geometry of the entire component in a single molding process during production. For this purpose, for example, the grained structure and component geometry are introduced as a negative into a mold, the plastic skin is shaped by sintering or spraying processes and then the molded skin is removed.
Both the web material and the molded skins are generally provided on the rear side with a layer of plastic foam, either after the embossing and/or after bringing and thermoforming them into the component mold (web material) or already in the tool mold in which the plastic skin was produced (molded skins). Of course, other methods of foam coating, such as for instance brushing methods, are known. By this subsequent “foam backing,” an already quite rigid three-dimensionally shaped component is obtained. Foam backing here represents only one possible way of forming a support structure for the plastic skin. Also known for instance is the adhesive attachment of supporting structural elements made of hard plastic.
U.S. Pat. No. 7,192,543 describes a method for producing out of tool melted/molded articles, such as for instance dashboards, door panels, or glove compartments, in which a divided lower mold is first, and at least partially, lined with a flexible film, which covers over the seams that are present in the mold, and which has on its inner side a grain effect, for example a leather texture. A reactive mixture is sprayed onto the flexible film and then forms the outer skin of the component, before further reinforcements or layers of foam are applied by various spraying or melt-molding methods.
After the production process, the molded skins with the support structure are usually given a clean finish, that is, any edges of skin are cut off and, in the case of dashboards, for example, the necessary recesses or holes for instruments, switches, decorative strips, radios, lighting means, et cetera are produced. After that, for example, all the switches and lighting means are individually fitted into the dashboard and wired or provided with connecting lines, which can then be connected when they are installed in the vehicle. The same applies to the installation of instruments, loudspeakers, and the like. Decorative strips and mountings must likewise also be attached.
Altogether, therefore, considerable effort, a series of time-consuming and cost-intensive production steps, and logistical planning are still required before a ready-to-install dashboard, a door insert, or similar components with functional elements are passed on to the plant carrying out further processing, that is to the vehicle manufacturer.
To minimize this production expenditure, it has been proposed to connect, that is, essentially to coat or laminate, electric conductors or thin film circuits, that is, films provided with thin vaporized or affixed metallic conductors, directly to the rear side of the molded skins or films before or after the foam backing.
In particular, in the inclusion of conductors for illuminants, which due to the required current rating have to be designed relatively “thick”, there arises the problem that when joining the two different materials (molded skins or films and conductors) the surface of decorative design, that is, the surface of the plastic skin which is visible from outside, is damaged by the contact pressure.
Furthermore, “thick” conductors will leave marks on the surface of the decorative design if they are laminated at temperatures that are too high and if they are laminated to one another, with the shrinkage of the materials being different, and subsequently cool down at different rates.
Furthermore, there exists the problem that the molded skins or films and the conductors have different heat expansion coefficients when stored in heat, and thus a second conductor which might have been laminated behind the surface of the decorating design becomes visible.
In addition, there exists the problem that certain areas of the surfaces, especially in the case of surfaces that are produced by the slush process (rotational sintering), cause kinks during demolding due to their different degrees of rigidity.
It has been proposed already to apply electroluminescent elements or layers in or on components and/or lining parts for the interior of motor vehicles.
For instance, CA 2 454 911 A1 discloses a roof lining as a molding, which is provided with strip-shaped electroluminescent elements. The roof lining consists of a molded carrier which is grouted with a coating film to form a component. Prior to grouting, the electroluminescent elements are positioned in the carrier, passed with their connecting cables through the carrier, and are subsequently covered, fixed, and grouted with the applied coating film. The various necessary positioning and pressing steps in the tools required for this purpose prove to be disadvantageous. In addition, in this embodiment the electroluminescent elements can also become visible behind the surface of the decorative design/coating film.
DE 10 2005 038 680 A1 discloses a component of a motor vehicle having a three-dimensional surface which comprises an electroluminescent layer and is back-injection-molded with a thermoplastic plastic material in order to fix the component mold. Thus, essentially smaller non-flexible illuminants such as illuminated push-buttons or luminous elements are produced. The production of larger parts is rather difficult by this embodiment.